Spinal deformity correction

ABSTRACT

A spinal alignment system can include a rod and a plurality of uniplanar screw assemblies that include a screw, a cap, and a housing. The screw and cap can be configured such that the relative angular displacement between the screw and the cap is limited to a first limit angle in a first plane and to a second limit angle in a second plane that is perpendicular to the first plane, the second limit angle being larger than the first limit angle. The housing can be coupled to the cap and configured to maintain the cap in proximity with the head of the screw. The housing can have two elongated elements forming a U-shaped saddle. The alignment system can also include a plurality of locking cap assemblies that capture the rod within the U-shaped saddle and are tightened to fixedly couple the rod to the respective uniplanar screw assemblies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/639,846, filed on Dec. 21, 2012, which is the U.S. National Phaseunder 35 U.S.C. §371 of International Application No. PCT/US2011/031267,filed on Apr. 5, 2011, which claims the benefit of U.S. ProvisionalPatent Application No. 61/321,250, filed on Apr. 6, 2010. The entirecontents of each of these applications are herein incorporated byreference.

BACKGROUND

1. Field

The present disclosure generally relates to systems and methods forcorrecting spinal deformities.

2. Description of the Related Art

The treatment of spinal deformity requires a three dimensional approachand therefore is organized into three primary planes of correctionrelative to the human body. These three planes include the frontal orcoronal plane, the sagittal or lateral plane, and the transverse oraxial plane as shown in FIG. 1. Correction and proper alignment of thesethree planes is often the goal of the surgeon in the treatment of spinaldeformity. Spinal deformities of varying etiologies are well known.

Over the past several decades, spinal fusion has been chosen as thestandard of practice in the treatment of spinal deformity. Spinal fusionis the implantation of a rigid construct that may include rods, bonescrews, hooks, and wires.

Early treatment of spinal deformity, more specifically scoliosis,involved a Harrington Rod developed by Dr. Paul Harrington. During thisparticular procedure, the Harrington rod is implanted along the spinalcolumn to treat, among other conditions, a lateral or coronal planecurvature of the spine. With this procedure, no special attention wasmade to treat the sagittal or axial planes of alignment and as a result“Flatback Syndrome” developed whereby the spine progressively grew intoan unnatural, straightened position with limited lordosis.

Years later, Dr. Yves Cotrel and Professor Jean Dubousset attempted toaddress all three aspects of planar management (i.e. Coronal, Sagittaland Axial) in the treatment of spinal deformity with theCotrel-Dubousset (C-D) technique which was later modified by the TexasScottish Rite Hospital (TSRH) in 1985. Both the C-D and the TSRHtechniques required a curved rod and hooks as a spinal fusion construct.Furthermore, the C-D and TSRH technique required that a curved rod berotated 90 degrees onto its side, utilizing the kyphosis and lordosis ofthe contoured rod to match the convexity and concavity of the spinaldeformity. Once secured, the rod is then rotated to correct the coronaland sagittal balances of the spinal deformity. Subsequently, the C-D orTSRH technique failed to correct the axially unbalanced vertebra. As aresult of the unaddressed axial balance, the patient is left with unevenshoulders or hips, also known as “Rotational Trunk Shift.”

SUMMARY

In view of the shortcomings of the existing procedures for treatingspinal deformities, there is a need for improvements which allow for themanagement of all three deformity planes in an effort to maximize acomplete spinal deformity correction. It is desirable to not only manageall three deformity planes but allow for a de-rotation system to beassembled quickly with superior rigidity.

The disclosed system provides a method and system for correcting spinaldeformities with special attention made for the coronal, sagittal, andaxial planes. From an implant standpoint, uni-planar or monoaxialpedicle screws provide the surgeon with a rigid base by which thesurgeon can cantilever against during the axial derotation maneuver.From an instrument standpoint, derotation tubes or restraint sleeves canbe attached to either uniplanar or polyaxial screw assemblies to providethe surgeon with an extended element that can be controlled andmanipulated during spinal derotation. Handles can be attached to thederotation tubes and restraint sleeves to provide further control andincreased leverage to derotate the spine. Certain disclosed methods forderotating the spine using derotation tubes or restraint sleeves connectand control the derotation tubes and/or restraint sleeves as a singlecluster in order to spread the concentration of forces involved with anaxial correction. The disclosed system allows for a quick and rigidassembly of a derotation cluster.

In certain embodiments, a fastening system is disclosed that includes ascrew having a head and a threaded portion that lies in both a firstplane and a second plane that is perpendicular to the first plane. Thefastening system also includes a cap configured to engage the head ofthe screw such that when the cap is engaged with the screw, the relativeangular displacement between the threaded portion and the cap is limitedto a first limit angle in the first plane and to a second limit angle inthe second plane, the second limit angle being larger than the firstlimit angle.

In certain embodiments, a screw assembly is disclosed that includes ascrew comprising a head and a threaded portion that lies in both a firstplane and a second plane that is perpendicular to the first plane. Thescrew assembly also includes a cap configured to engage the head of thescrew such that when the cap is engaged with the screw, the relativeangular displacement between the threaded portion and the cap is limitedto a first limit angle in the first plane and to a second limit angle inthe second plane, the second limit angle being larger than the firstlimit angle, and a housing coupled to the cap, the housing configured tomaintain the cap in proximity with the head of the screw.

In certain embodiments, an alignment system is disclosed that includes afirst rod and a plurality of uniplanar screw assemblies that eachcomprise a uniplanar screw comprising a head and a threaded portion thatlies in both a first plane and a second plane that is perpendicular tothe first plane, a uniplanar cap configured to engage the head of theuniplanar screw such that when the uniplanar cap is engaged with theuniplanar screw, the relative angular displacement between the threadedportion and the uniplanar cap is limited to a first limit angle in thefirst plane and to a second limit angle in the second plane, the secondlimit angle being larger than the first limit angle, and a housingcoupled to the uniplanar cap, the housing configured to maintain theuniplanar cap in proximity with the head of the uniplanar screw, thehousing comprising two elongated elements forming a U shaped saddle thatis configured to accept the first rod, at least one elongated elementcomprising threads on a portion of the surface facing the otherelongated element. The alignment system also includes a plurality oflocking cap assemblies. Each locking cap assembly comprises a slidingelement configured to fit around both elongated elements and slide alongthe elongated elements and a threaded element disposed within thesliding element and configured to engage the threads of the at least oneelongated element. The first rod is configured to engage the pluralityof uniplanar screw assemblies by moving laterally into the U-shapedsaddle of the housings of the uniplanar screw assemblies. The pluralityof locking cap assemblies are configured to be coupled to the housing soas to capture the first rod within the U-shaped saddle of the housingand, when the threaded element of the locking cap assembly is actuated,to displace the first rod along the U shaped saddle until the first rodis in contact with a bottom of the U-shaped saddle and then fixedlycouple the first rod to the respective uniplanar screw assemblies.

In certain embodiments, an alignment system is disclosed that includes arod and a plurality of polyaxial screw assemblies, each comprising apolyaxial screw comprising a head and a threaded portion that lies inboth a first plane and a second plane that is perpendicular to the firstplane, a polyaxial cap configured to engage the head of the polyaxialscrew such that when the polyaxial cap is engaged with the polyaxialscrew, the relative angular displacement between the threaded portionand the polyaxial cap is at least limited to a first limit angle in boththe first and second planes, and a housing coupled to the polyaxial cap,the housing configured to maintain the polyaxial cap in proximity withthe head of the polyaxial screw, the housing comprising two elongatedelements forming a U shaped saddle that is configured to accept the rod.At least one elongated element comprises threads on a portion of thesurface facing the other elongated element. The alignment system alsoincludes a plurality of locking cap assemblies. Each locking capassembly comprises a sliding element configured to fit around bothelongated elements and slide along the elongated elements and a threadedelement disposed within the sliding element and configured to engage thethreads of the at least one elongated element. The alignment system alsoincludes a plurality of restraint sleeves that are configured toslidably couple to the housings of respective polyaxial screw assembliesand engage the rod and extend above the housings and a plurality ofrestraint shafts configured to engage a pocket on the head of thepolyaxial screw thereby aligning the threaded portion of the polyaxialscrew with the restraint shaft and secure the respective restraintsleeves to the respective housings. The rod is configured to engage theplurality of polyaxial screw assemblies by moving laterally into theU-shaped saddle of the housings of the polyaxial screw assemblies. Theplurality of locking cap assemblies are configured to be coupled to thehousing so as to capture the rod within the U-shaped saddle of thehousing and, when the threaded element of the locking cap assembly isactuated, to displace the rod along the U shaped saddle until the rod isin contact with a bottom of the U-shaped saddle and then fixedly couplethe rod to the respective polyaxial screw assemblies.

In certain embodiments, a method of en-bloc correction of spinaldeformity of a patient is disclosed. The method comprises the step ofattaching a plurality of first screw assemblies each comprising ahousing having two elongated elements forming a U-shaped saddle whereinat least one elongated element comprises threads on a portion of thesurface facing the other elongated element, a screw comprising a headand a threaded portion, and a cap configured to engage the head of thescrew such that when the cap is engaged with the screw, the relativeangular displacement between the threaded portion and the cap is limitedto a first limit angle in a first plane and to a second limit angle in asecond plane that is perpendicular to the first plane, the second limitangle being larger than the first limit angle, to a plurality of spinalvertebrae of the patient. The method also comprises the steps of placinga first rod transversely across the U-shaped saddles of a portion of thefirst screw assemblies, placing a plurality of locking screw assemblieshaving a sliding element configured to fit around both elongatedelements and slide along the elongated elements and a threaded elementdisposed within the sliding element and configured to engage the threadsof the at least one elongated element over the respective U-shapedsaddles of the housings so as to capture the first rod within theU-shaped saddles of the housings, actuating the threaded element of thelocking screw assemblies to displace the first rod along the respectiveU-shaped saddles until the first rod is in contact with a bottom of theU-shaped saddle, and tightening the threaded element of the lockingscrew assemblies to fixedly couple the respective first screw assembliesto the first rod.

In certain embodiments, a method of en-bloc correction of spinaldeformity of a patient is disclosed. The method comprises the step ofattaching a plurality of polyaxial screw assemblies each comprising ahousing having two elongated elements forming a U shaped saddle whereinat least one elongated element comprises threads on a portion of thesurface facing the other elongated element, a polyaxial screw comprisinga head and a threaded portion that lies in both a first plane and asecond plane that is perpendicular to the first plane, and a polyaxialcap configured to engage the head of the polyaxial screw such that whenthe polyaxial cap is engaged with the polyaxial screw, the relativeangular displacement between the threaded portion of the polyaxial screwand the polyaxial cap is at least limited to a first limit angle in boththe first and second planes, to a plurality of spinal vertebrae of thepatient. The method also comprises the steps of placing a rodtransversely across the U-shaped saddles of the housings of thepolyaxial screw assemblies, and placing a plurality of locking screwassemblies having a sliding element configured to fit around bothelongated elements and slide along the elongated elements and a threadedelement disposed within the sliding element and configured to engage thethreads of the at least one elongated element over the respective Ushaped saddles of the housings of the polyaxial screw assemblies so asto capture the rod within the U shaped saddles of the housings. Themethod also comprises the steps of coupling a plurality of restraintsleeves to the housings of respective polyaxial screw assemblies, andactuating a plurality of restraint shafts to respectively engage apocket on the head of the polyaxial screws thereby aligning the threadedportion of the polyaxial screws with the respective restraint shaft andsecure the respective restraint sleeves to the respective housings. Themethod also comprises the steps of actuating the threaded elements ofthe locking screw assemblies to displace the rod along the respectiveU-shaped saddles of the housings of the polyaxial screw assemblies untilthe rod is in contact with a bottom of the U shaped saddles of thepolyaxial screw assemblies, and tightening the threaded elements of thelocking screw assemblies to fixedly couple the respective polyaxialscrew assemblies to the rod.

In certain embodiments, a handle for a surgical tool is disclosed. Thehandle includes a body having a passage and a handle post that includesa coupler having an open cannula configured to engage the surgical tooland a shaft fixedly attached to the coupler, the shaft having a borethat passes into the open cannula of the coupler, the shaft alsoconfigured to pass through the passage of the body. The handle alsoincludes a locking assembly that includes a locking nut and a lockingnut post fixedly attached to the locking nut and configured to engagethe bore of the handle post shaft. Rotating the locking nut relative tothe handle post shaft advances the locking nut post through the bore ofthe handle post shaft and into the open cannula of the coupler to securethe handle to the surgical tool.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide furtherunderstanding and are incorporated in and constitute a part of thisspecification, illustrate disclosed embodiments and together with thedescription serve to explain the principles of the disclosedembodiments. In the drawings:

FIG. 1 is a diagram of the three reference planes of the human body.

FIG. 2A is a lateral view of the spinal column and its regions.

FIG. 2B illustrates the structure of an exemplary spine.

FIGS. 3A and 3B show a patient with a normal spine and a patient withscoliosis.

FIGS. 4A-4C illustrate a screw according to certain embodiments of thepresent disclosure.

FIGS. 5A-5C illustrate a cap according to certain embodiments of thepresent disclosure.

FIGS. 6A-6C are various views of a housing according to certainembodiments of the present disclosure.

FIGS. 7A-7D are various views of a screw assembly according to certainembodiments of the present disclosure.

FIGS. 8A-8D depict the motion of a screw assembly according to certainembodiments of the present disclosure.

FIGS. 9A-9E illustrate another embodiment of a screw assembly accordingto certain embodiments of the present disclosure.

FIGS. 10A-10D are various views of a locking screw assembly according tocertain embodiments of the present disclosure.

FIGS. 11A-11D depict the formation of an alignment system according tocertain embodiments of the present disclosure.

FIGS. 12A and 12B illustrate initial and final engagements of a cap witha screw assembly according to certain embodiments of the presentdisclosure.

FIGS. 13A and 13B depict a derotation tube, a retaining post, and ahandle according to certain embodiments of the present disclosure.

FIG. 14 is an exploded isometric view of the handle of FIG. 13Aaccording to certain embodiments of the present disclosure.

FIG. 15A depicts a hex drive assembly used to tighten the threadedelement of the locking cap assembly according to certain embodiments ofthe present disclosure.

FIG. 15B is an isometric view of the derotation tube of FIG. 13Athreadably coupled to one of the screw assemblies of the alignmentsystem of FIG. 11D according to certain embodiments of the presentdisclosure.

FIG. 16 is an isometric view of multiple derotation assemblies accordingto certain embodiments of the present disclosure.

FIG. 17A is an isometric view of a lateral construct assembly accordingto certain embodiments of the present disclosure.

FIG. 17B is an isometric view of a retaining clip assembly according tocertain embodiments of the present disclosure.

FIGS. 18A and 18B depict the components of another embodiment of aderotation tube according to certain embodiments of the presentdisclosure.

FIG. 18C is an exploded isometric view of a derotation assemblyaccording to certain embodiments of the present disclosure.

FIGS. 18D-18F depict a lateral construct assembly incorporating multiplederotation assemblies of FIG. 18C and a retaining clip assembly of FIG.17B according to certain embodiments of the present disclosure.

FIG. 19 depicts two lateral construct assemblies arranged on the leftand right sides of a spinal column according to certain embodiments ofthe present disclosure.

FIG. 20 depicts two lateral construct assemblies joined by two retainingclip assemblies to form a derotation cluster according to certainembodiments of the present disclosure.

FIGS. 21A-21C depict a derotation sleeve assembly according to certainembodiments of the present disclosure.

FIG. 22 depicts another derotation cluster formed from a lateralconstruct assembly and multiple derotation sleeve assemblies accordingto certain embodiments of the present disclosure.

FIGS. 23A-23B are perspective views of a polyaxial screw and capaccording to certain embodiments of the present disclosure.

FIGS. 23C-23D are front and side views of the polyaxial screw assemblyaccording to certain embodiments of the present disclosure.

FIGS. 24A-24C depict the insertion of a second rod using the derotationcluster of FIG. 22 according to certain embodiments of the presentdisclosure.

DETAILED DESCRIPTION

The following description discloses embodiments of screw assemblies,derotation assemblies, lateral constructs, and derotation clusters thatare to be used by surgeons to correct spinal deformity in the threeprimary planes of the human body. These various components andassemblies can be employed in multiple combinations and techniquesdepending on the condition of the patient and the preferences of thesurgeon.

In the following detailed description, numerous specific details are setforth to provide a full understanding of the present disclosure. It willbe apparent, however, to one ordinarily skilled in the art thatembodiments of the present disclosure may be practiced without some ofthe specific details. In other instances, well-known structures andtechniques have not been shown in detail so as not to obscure thedisclosure.

For the purpose of the present disclosure, the term “derotation” refersto the method by which the axial or transverse balance of a deformitycurve is restored.

For the purpose of the present disclosure, a “lateral construct”comprises, but is not limited to, rods, bone screws, and locking capsjoined together for the purpose of fusing more than one vertebratogether.

For the purpose of the present disclosure, the term “cluster” refers toa series of derotation tubes that are connected to one another bothlaterally and bi-laterally with respect to the fusion construct.

For the purpose of the present disclosure, the term “polyaxial” refersto the ability of one element, such as the threaded portion of a screw,to deflect a significant amount, i.e. greater than 10 degrees, in alldirections relative to a coupled housing.

For the purpose of the present disclosure, the term “uni-planar” refersto the ability of one element, such as the threaded portion of a screw,to deflect a significant amount, i.e. greater than 10 degrees, in oneplane relative to a coupled housing and a limited amount, i.e. less than5 degrees, in a perpendicular plane.

For the purpose of the present disclosure, the term “monoaxial” and“uniaxial” refers to the ability of one element, such as the threadedportion of a screw, to not deflect relative to a second element, such asthe coupled housing.

Certain embodiments of the present disclosure provide a lateralconstruct that is implanted on the posterior side of the patient for thetreatment of spinal deformity. Certain embodiments of the lateralconstruct include screws that are rotatably coupled to elongatedU-shaped housings to form screw assemblies. In certain embodiments, thethreaded portion of the screw can move polyaxially with respect to thehousing. In certain embodiments, the threaded portion of the screwarticulates in a uni-planar motion. In certain embodiments, theuni-planar screw design is controlled by the interface between the screwhousing and a cap whereby certain flats on the receiving end of the capare paired with similar flats on the screw body.

In certain embodiments, the screws are implanted within the pedicles ofselected vertebrae along the deformity curve of the spine. Onceimplanted, a rod is inserted into the U-shaped saddle of the screwassembly. The rod is secured to each of the implanted screws using athreaded locking screw assembly. In certain embodiments the elongatedtravel of the U-shaped saddle of the housing allows the surgeon tosegmentally reduce the locking screw assembly in a controlled fashion.

In certain embodiments, the surgeon bends the rod in-situ to configurethe sagittal balance. In certain embodiments, the surgeon uses apre-contoured rod to achieve the sagittal balance of the deformitycurve. Once the rod is reduced at each level by incrementally tighteningthe locking screw assemblies of the implanted screws, the coronal andsagittal balance of the scoliotic spine are restored.

In certain embodiments, the surgeon utilizes a rod on a single lateralside of the construct to gain sagittal, coronal, and axial alignment. Incertain embodiments, the surgeon uses two rods, arranged bi-laterally,to gain sagittal, coronal, and axial correction.

Once the coronal and sagittal alignments have been achieved, the axialor transverse alignment is next to be addressed. In certain embodimentsof the present invention, derotation tubes are anchored at the proximalend of the elongated bone screw housing through a threaded derotationtube retaining post. In certain embodiments, the derotation tubes havemodular handles attached to them for added derotation leverage.

Once anchored, the derotation tubes are joined together on a lateralside of the construct using a retaining clip. In certain embodiments,the retaining clip is comprised of two arms that are rotatably coupledto one another. A latch or quick release mechanism is used to secure thearms of the retaining clip in the closed, clamped, position. In certainembodiments, the retaining clip includes a compressible core thatfunctions to increase the grip strength when multiple derotation tubesare attached as one.

In certain embodiments, the derotation tubes are cylindrical with aknurled surface to increase the grip strength with the compressible coreof the retaining clip. Certain embodiments of the derotation tube havemultiple flat surfaces designed to decrease rotation and increasealignment during the placement of the retaining clip. Derotation tubelocking nuts are threaded onto such embodiments of the derotation tubesand tightened onto the assembled retaining clip to limit rotation andtranslation amongst adjoining derotation tubes. In certain embodiments,the derotation tubes and derotation tube locking nuts have single ormulti-lead threads. Translation and rotation of adjoining derotationtubes are avoided to maintain a rigid cluster; necessary to derotate thespine in restoring axial balance. In certain embodiments, the retainingclip is used to rigidly connect more than one of the derotation tubesinto a rigid subset on a bi-lateral side of the construct. In otherembodiments, the retaining clip is used to rigidly connect more than oneof the derotation sleeve assemblies on a bi-lateral side of theconstruct.

In certain embodiments, a second retaining clip is connectedtransversely to rigidly connect both sides of the said bi-lateralconstruct to form a single rigid cluster. In certain embodiments, thesingle rigid cluster includes a bi-lateral construct comprised ofderotation tubes and another bilateral construct comprised of derotationsleeve assemblies. In certain embodiments, the single rigid clusterincludes two bi-lateral constructs both comprised of derotation tubesonly.

In certain embodiments, the bi-lateral construct may only consist ofderotation sleeves on one side of the construct and a captured rod onthe opposite side of the construct by which derotation is performeduni-laterally rather than bi-laterally.

Once formed, the single rigid cluster acts as a rigid proximalconnection whereby pure rotation about the proximal handles istranslated into pure rotation about the distal construct.

In certain embodiments, derotation constitutes derotating one clusterrelative to another cluster. In certain embodiments, one or moreclusters are attached along the spinal deformity at different endpointsof the spine. Axial correction is gained whereby two clusters arederotated in the opposite direction of one another.

In certain embodiments, an elongated retaining clip or stabilization armis used to hold the position of the derotated clusters while the screwsare fully secured to the rod through the final tightening of the lockingscrew assemblies.

FIG. 1 is a diagram of the three reference planes of the human body 10.These three planes include the coronal, or frontal, plane 22, whichpasses from left to right through the body. The sagittal, or lateral,plane 20 passes from front to back. The transverse, or axial, planepasses horizontally, for a standing person, through the body.

FIG. 2A is a lateral view of the spinal column 12 and its regions. Fromthe neck down, the spinal regions are the cervical region, the thoracicregion, the lumbar region, the sacrum, and the coccyx. There are twotypes of curves in the spine: kyphosis (the spine curves inwards) andlordosis (the spine curves outwards). In a normal spine, the cervicaland lumbar regions have a lordotic curve 28, while the thoracic regionand sacrum have a kyphotic curve 26.

FIG. 2B illustrates the some of the structure of the spine. The spineincludes a stacked series of vertebra 14 separated by discs 16. Many ofthe vertebrae 14 have flanges and protrusions, one of which is thepedicle 18 that is present on both sides of the vertebral body 14A.

FIGS. 3A and 3B show a patient 10A with a normal spine and a patient 10Bwith scoliosis. As viewed from the back in FIG. 3A, the spine 12 ofpatient 10A follows a straight line 30 in the coronal plane 22. Thespine 12 of patient 10B in FIG. 3B exhibits a double curve 32 in thecoronal plane 22. Other patients may have curvature or offsets from theideal spinal shape shown in FIG. 2A in the sagittal plane 20 ortransverse plane 24.

FIGS. 4A-4C illustrate a screw 40 according to certain embodiments ofthe present disclosure. Screw 40, also referred to as a bone screw orpedicle screw, has a head 42 and a threaded portion 44. FIGS. 4A and 4Bare perpendicular lateral views of screw 40, while FIG. 4C is aperspective view of the head 42. The head 42 has a spherical surface 46and a hexagonal pocket 50 suitable for receiving a hex-drive driver (notshown). The head 42 also includes, in this embodiment, a pair of flatsurfaces 48 separated by a distance 49. As will be discussed in moredetail with respect to FIGS. 7A-7C, these flat surfaces 48 are a part ofthe features that result in this particular embodiment being referred toas a uni-planar screw. The threaded portion 44 is, in this embodiment,configured with screw threads that are suitable for engagement withhuman spinal bone.

FIGS. 5A-5C illustrate a cap 60 according to certain embodiments of thepresent disclosure. FIG. 5A is a perspective view of cap 60, while FIG.5B is a cross-section taken through the center of the cap 60 and FIG. 5Cis a lateral external view of cap 60. The cap 60 has a body 62 with acentral bore having a series of steps 64 that, as can be seen in FIG.7D, are configured to engage the spherical surface 46 of the screw 40.Cap 60, in this embodiment, has two ears 66 that protrude below the body62. Each ear 66 has a flat surface 67, with the two flat surfaces 67separated by a distance 69. The body 62 also, in this embodiment, has apair of blind notches 65 the function of which is described in moredetail with regard to FIGS. 6A and 6C.

FIGS. 6A-6C are various views of a housing according to certainembodiments of the present disclosure. FIGS. 6A and 6B are perpendicularlateral views of housing 72, while FIG. 6C is a cross-section of housing72 taken along line C-C in FIG. 6B. The housing 72 has a base 74 with,in this embodiment, two elongated elements 76 that form a U-shapedsaddle of the housing 72. The base 74 has a central vertical bore (notvisible). A lip 75 is located at the lower edge of the bore, reducingthe bore to a dimension that is less than the diameter of the head 42 ofthe screw 40. In this embodiment, the interior surface of each elongatedelement 76 has threads 77, as seen in FIG. 6C. There is a hole 78penetrating through the housing 72 that is discussed in more detail withrespect to FIGS. 7A and 7C. Each elongated element 76 has, in thisembodiment, a groove 79 that will be discussed in more detail withrespect to FIG. 11D.

FIGS. 7A-7D are various views of a screw assembly 70 according tocertain embodiments of the present disclosure. FIG. 7A shows an explodedview of the components of screw assembly 70, including cap 60, screw 40,housing 72, and two pins 80. To assemble the screw assembly, the screw40 is inserted between the elongated elements 76 and through the bore ofthe base 74 until the spherical surface 46 of screw 40 rests on the lip75 of housing 70. The cap 60 is then placed over the head 42 within thebore of housing 70 and the two pins 80 are pressed into place in holes78, thereby retaining the cap 60 in the housing 70 while allowing thescrew 40 to rotate relative to the housing 70.

FIG. 7B is an enlarged view of the portion of FIG. 7A encircled by thebroken-line circle 7B. When engaged as shown in FIG. 7A, the ears 66 ofcap 60 are positioned such that, in this embodiment, the two surfaces 67of the cap 60 are positioned adjacent to the two surfaces 48 of thescrew 40.

FIG. 7C is a cross-section through the center of the assembled screwassembly 70, taken through the two pins 80. It can be seen how the pins80 engage the blind holes 65 of the cap 60. In certain embodiments, pins80 are press fit into the housing 72. In certain embodiments, anadhesive (not shown) is used to fix the pins 80 in housing 72. It isalso visible herein how the surfaces 67 of cap 60 are aligned andadjacent to surfaces 48 of screw 40. The clearance between the surfaces67 and surfaces 48 is controlled by the dimensions 49 and 69 of thescrew 40 and cap 67, respectively. As will be discussed more fully withrespect to FIGS. 8A-8D, a small amount of clearance allows a smallamount of rotation of screw 40 with respect to cap 60 which is fixed, inan assembled screw assembly 70, relative to housing 72.

FIG. 7D is a cross-section through the center of the assembled screwassembly 70, taken at a right angle to the view of FIG. 7C. In thisview, the spherical bearing formed by the combination of the steps 64 ofcap 60 and the lip 75 of the housing 70 capturing the spherical surface46 of screw 40. As the plane of the cross-section of FIG. 7D is parallelto the flat surfaces 48 and 67, screw 40 is allowed to rotate in theplane of the cross-section up to the point where the threaded portion 44of the screw 40 contacts the base 74 of the housing 70.

FIGS. 8A-8D depict the motion of a screw assembly 70 according tocertain embodiments of the present disclosure. FIG. 8A shows the screwassembly 70 in an “aligned” configuration, wherein both the housing 72and the threaded portion 44 of screw 40 are coincident with an axis 86.FIG. 8D is a top view of screw assembly 70 that shows how axis 86 isformed by the intersection of mutually perpendicular first plane 82 andsecond plane 84.

FIG. 8B illustrates the range of motion of screw assembly 70 in firstplane 82. As previously discussed with respect to FIG. 7C, the clearancebetween the flat surfaces 67 and flat surfaces 48 of the screw 40 andcap 60, respectively, allow angular displacement of screw 40 withrespect to the housing 72 up to a first limit angle 90 in bothdirections away from the aligned position of FIG. 8A.

FIG. 8C illustrates the range of motion of screw assembly 70 in secondplane 84 that is aligned with the flat surfaces 67 of cap 60 and, as aresult of the pins 80, also with the elongated elements 76 of housing72, respectively. Screw 40 can have an angular displacement with respectto the housing 72 up to a second limit angle 92 in both directions awayfrom the aligned position of FIG. 8A.

FIG. 8D is a top view of screw assembly 70 showing the limits of angulardisplacement in first plane 82 and second plane 84 as well as therelation of axis 86 to mutually perpendicular planes 82 and 84.

FIGS. 9A-9E illustrate another embodiment of a screw assembly 70Aaccording to certain embodiments of the present disclosure. The screwassembly 70 of FIGS. 8A-8D had a large range of motion in plane 84,being parallel to the direction that a rod would pass through theU-shaped saddle of the housing 72, and a reduced range of motion inplane 82. FIGS. 9A and 9B are front and side views of a screw assembly70A that has the large range of motion in plane 82 and a reduced rangeof motion in plane 84. This alternate configuration of ranges of motionis accomplished by cap 60A that is a modification of cap 60 of FIGS.5A-5C, wherein the ears 66 are rotated by 90 degrees relative to theblind notches 65. When the screw assembly 70A is assembled, the ears 66of cap 60A are located by the pins 80 to be perpendicular to theU-shaped saddle of housing 80, thereby rotating the large and reducedranges of motion of screw assembly 70A by 90 degrees with respect to thescrew assembly 70.

FIGS. 10A-10D are various views of a locking screw assembly 100according to certain embodiments of the present disclosure. FIG. 10A isan exploded view of the components of locking screw assembly 100,including a sliding element 102 having an interior space 103 with a lip(not shown) at the bottom edge of the interior space 103. Slidingelement 102 also has a pair of notches 108 the function of which will bediscussed in more detail with respect to FIG. 10B. The locking screwassembly 100 also includes a threaded element 104 and a retentionelement 106. To assemble the locking screw assembly 100, the threadedelement 104 is placed into the interior space 103, where the threadedelement 104 rests on the lip, and retention element 106 is, in thisembodiment, pressed into notches 105 on the two sides of interior space103. In certain embodiments, the retention element 106 is bonded tosliding element 102. FIGS. 10B-10D are top, front, and bottom views,respectively, of locking screw assembly 100.

FIGS. 11A-11D depict the formation of an alignment system 110 accordingto certain embodiments of the present disclosure. FIG. 11A is a frontview of multiple screw assemblies 70 and a rod 112 whereby the rod 112is located within the U-shaped saddle of the screw assemblies 70. Inthis embodiment, the rod 112 is pre-curved with lordotic curve 28 and akyphotic curve 26 in the sagittal plane.

FIGS. 11B and 11C are top and side views, respectively, of a rod 112.FIG. 11B illustrates a rod 112 having a longitudinal line 114 scribed onone side to provide a reference for the orientation of the pre-bent rod112. Being able to orient the rod 112 from the start of the surgery willgive the surgeon an idea of the position of the spine and or the amountof correction needed to derotate the spine back to an anatomicallycorrect position.

FIG. 11C shows how exemplary rod 112 is pre-bent, in this embodiment,into a 120 degree thoracic kyphotic curve 119 and a 125 degree lumbarlordotic curve 117. The rod 112, in this embodiment, has a transitionindicator mark 116 that denotes the point of transition from thekyphotic curve 119 to the lordotic curve 117. This embodiment of rod 112also has transverse indication marks 118, starting at the transitionpoint and extending outward in both directions. Transverse indicationmarks 118 eliminate the need for the surgeon to manually measure the rod112 based on measurements from a rod template (not shown) when cuttingthe rod 112. In certain embodiments, the transverse indication marks 118are marked with serially numbered indicators (not shown). Since rods 112are placed in the patient one at a time and cut to length during thesurgery, transverse indication marks 118 with serially numberedindicators allow the second rod to be cut without additional measuring,thereby saving time and effort during the surgery. In certainembodiments, the numbering scheme of the serially numbered indicators iscentered at the transition indicator mark 116. In certain embodiments,the serially numbered indicators increase in both directions away fromthe transition indicator mark 116.

FIG. 11D shows the configuration of FIG. 11A with the addition ofmultiple locking cap assemblies 100 that are threadably coupled to therespective housings 72 of screw assemblies 70 by the threaded element104 (not visible), forming an alignment system 110 that may be used togain sagittal and coronal alignment for a patient.

After provisionally securing the rod in the screw assemblies 70 butbefore fully tightening the locking cap assemblies 100, the surgeon mayrotate the rod using additional tools (not shown) until the desiredcorrection is achieved in one or both of the coronal and sagittalplanes. In certain embodiments, a surgeon may use two alignment systems110, arranged bi-laterally on the spine, to gain sagittal and coronalcorrection. If no further manipulation is required, the locking capassemblies 100 can be fully tightened to lock the housings 72 to thescrew 40 in the current orientation, and the tops of the elongatedelements 76 can be broken off at the grooves 79 shown in FIG. 6B.

FIGS. 12A and 12B illustrate initial and final engagements of a lockingcap assembly 100 with a screw assembly 70 according to certainembodiments of the present disclosure. In FIG. 12A, the rod 12 has beenplaced through the U-shaped saddle of screw assembly 70 at a mid-pointof the height of the slot. A locking cap assembly 100 has been placedover the elongate elements of screw assembly 70 and the threaded element104 (not visible) engaged with the threads 72 of the screw assembly 70.The threaded element 104 has been advanced until the sliding element 102is in contact with the rod 112. After all of the screw assemblies 70 ina procedure have received a locking cap assembly 100, as shown in FIG.11D, then the surgeon may incrementally advance the threaded elements104 of all of the screw assemblies 70 to reduce the position of the rod112 until it reaches the bottom of the U-shaped saddle, as shown in FIG.12B. Once in this position, the threaded element 104 can be tightened,thereby engaging the steps 64 of the cap 60 with the spherical surface46 of the screw 40 and locking the housing 72 and the screw 40 togetherin their present relative orientation.

FIGS. 13A and 13B depict a derotation tube 120, a retaining post 130,and a handle 140 according to certain embodiments of the presentdisclosure. The derotation tube 120 has an engagement sleeve 124 at thedistal end of a hollow tubular body 122. The engagement sleeve 124 isconfigured to slide over the proximal end of screw assembly 70 as isdiscussed in more detail with respect to FIG. 13B. The body 122 has, inthis embodiment, a hexagonal feature 128 at its proximal end with aknurled surface 126 adjacent. The function of the knurled surface 126 isdiscussed in more detail with respect to FIG. 17A. Together, thederotation tube 120, a retaining post 130, and a handle 140 form aderotation tube assembly 160.

Retaining post 130 has a body 132 with a threaded tip 134 at the distalend. The body 132 also has a hexagonal feature 136 at the proximal end.The body 132 and threaded tip 134 are sized such that they fit throughthe interior bore of derotation tube 120.

Handle 140 has a body 142 connected to a hexagonal tip 142 that isconfigured to engage the hexagonal feature 128 of the derotation tube120. The construction of the handle 140 is described in more detail withrespect to FIG. 14.

FIG. 13B is an enlarged cross-section of the engagement sleeve 124 inplace over the elongated elements 76 of screw assembly 70. Threadedelement 104 can be seen to be in contact with cap 60 over the screw head42, with the sliding element 102 around the outside of the elongateelements 76. The body 132 of the retaining post 130 is positionedbetween the elongate elements 76, with the threads of threaded tip 134engaged with the threads 77. When the retaining post 130 is tightenedwithin the derotation tube 120, the hexagonal feature 136 will seatagainst the hexagonal feature 128 of the derotation tube 120 and thetension developed between the engaged threaded tip 134 and the hexagonalfeature 136 holds the derotation tube in engagement with the screwassembly 70, and the slots in the side of the engagement feature 124 fitover the rod 112 and prevent rotation of the derotation tube 120 withrespect to the screw assembly 70.

FIG. 14 is an exploded isometric view of the handle 140 of FIG. 13Aaccording to certain embodiments of the present disclosure. The modularhandle post 146 is inserted into one end of the modular handle body 142,which has a coupler 144 attached at the other end, with the combinationof the modular handle locking nut post 148 and the modular handlelocking nut 149 being inserted and threadably coupled to the oppositeside of the modular handle body 142. As the modular handle locking nut149 is advanced, the fixedly attached modular handle locking nut post148 is driven through the open cannula of the modular handle post 142and into the open hexagonal opening of coupler 144 and is intended tosecure the modular handle assembly 146 to the mating proximal end of thederotation tube 11.

FIG. 15A depicts a hex drive assembly 150 used to tighten the threadedelement 104 of the locking cap assembly 100 according to certainembodiments of the present disclosure. The shaft 152 is sized to passthrough the bore of retaining post 130 and the drive tip 154 is sized toengage the internal hex feature of the threaded element 104 (notvisible).

FIG. 15B is an isometric view of the derotation tube 120 of FIG. 13Athreadably coupled to one of the screw assemblies 70 of the alignmentsystem 110 of FIG. 11D according to certain embodiments of the presentdisclosure. A hex driver assembly 150 is inserted through the retainingpost receiving end 136. The threaded element 104 is segmentallytightened to the rod 112 by using the hex driver assembly 150. Morespecifically, the hex tip 154 of the hex driver assembly 150 engages thefemale hex of the threaded element 104 within the locking cap assembly100. Handle 140 is attached to derotation tube 120 to prevent thetightening torque from twisting the screw assembly 70. Tightening thelocking cap assembly 100 will, as tightened, forces the rod 112 down theU-shaped channel of the housing 72 as described in FIGS. 12A-12B.

FIG. 16 is an isometric view of multiple derotation assemblies 160according to certain embodiments of the present disclosure. Thederotation assemblies 160 are coupled to rod 112.

FIG. 17A is an isometric view of the lateral construct assembly 200according to certain embodiments of the present disclosure. The lateralconstruct assembly 200 is formed of the multiple derotation assemblies160 of FIG. 16 with the addition of a retaining clip assembly 170. Theretaining clip assembly 170 is sized to fit around the derotation tubebody 122 and engage the knurled surfaces 126 of each of the derotationtubes 120. Once the retaining clip bolt 172 is engaged with theretaining clip nut 174 and tightened, the set of derotation tubes areconstrained from translating or rotating with respect to each other. Incertain embodiments, more than one retaining clip assembly 170 isinstalled.

FIG. 17B is an isometric view of a retaining clip assembly 170 accordingto certain embodiments of the present disclosure. The retaining clipassembly 170 has two arms 176 and 178 that are, in this embodiment,hingedly connected at one end and have a threaded retaining featurecomprising a retaining clip bolt 172 and a retaining clip nut 174coupled to arms 178 and 176, respectively. When the arms are closed andthe retaining clip bolt 172 is engaged with the retaining clip nut 174,tightening the retaining clip bolt 172 draws the arms 176 and 178 closertogether. Each arm has a compressible pad 177 disposed on the surfacefacing the other arm. When the retaining clip assembly 170 is engagedaround the knurled surfaces 126 of derotation tubes 120, thesecompressible pads 177 are in contact with the knurled surfaces 126 andprovide a non-slip engagement that resists the derotation tube 120 fromturning or sliding with respect to the retaining clip assembly 170.

FIGS. 18A and 18B depict the components of another embodiment of aderotation tube 180 according to certain embodiments of the presentdisclosure. The derotation tube is similar to the derotation tube 120but with body 182 having a plurality of flats 184 arranged around thecircumference of the body 182. In the embodiment of FIG. 18A, there arefour flats 184 evenly spaced around the circumference of the body 182.In certain embodiments, there are more than four flats 184. In certainembodiments, there are six flats 184. In certain embodiments, there areless than four flats 184. In certain embodiments, there are only twoflats 184. In certain embodiments, there is only a single flat 184. Thebody also comprises an interrupted series of threads 186 that arealigned across the flats 184.

FIG. 18B depicts a locking nut 188 sided and configured to engage theinterrupted threads 186 of derotation tube 182. In certain embodiments,the locking nut 188 is knurled on the outside to improve the grip by thesurgeon.

FIG. 18C is an exploded isometric view of a derotation assemblyaccording to certain embodiments of the present disclosure. Two lockingnuts 188 are engaged with the interrupted threads 186 and positionedtowards the distal and proximal ends of derotation tube 180. The sameretaining post 130 and handle 140 of FIG. 11A are used with derotationtube 180. Together, the derotation tube 180, retaining post 130, andhandle 140 form a derotation assembly 190.

FIGS. 18D-18F depict a lateral construct assembly 202 incorporatingmultiple derotation assemblies 190 of FIG. 18C and the retaining clipassembly 170 of FIG. 17B installed according to certain embodiments ofthe present disclosure. FIG. 18A is an isometric view of multiplederotation assemblies 190 coupled to rod 112 FIG. 18E depicts themultiple derotation assemblies 190 with a retaining clip assembly 170attached between the two locking nuts 188 on each derotation tube 180.The compressible surfaces 177 of the retaining clip assembly 170 are incontact with the flats 184, thereby preventing rotation of thederotation tubes 180 with respect to the retaining clip assembly 170. Incertain embodiments, more than one retaining clip assembly 170 isinstalled. In certain embodiments, more than two locking nuts 188 areinstalled on at least one derotation tube 180.

FIG. 18F depicts the configuration of the multiple derotation assemblies190 after the locking nuts 188 have been relocated to contact theretaining clip assembly 170. Together, the multiple derotationassemblies 190 and retaining clip assembly 170 form a lateral constructassembly 202. This embodiment of a lateral construct assembly 202provides the translation and rotation resistance of the lateralconstruct assembly 200 of FIG. 17A with the additional constraint thatthe retaining clip assembly 170 is restrained from sliding in the distalor proximal directions along any of the derotation tubes 180.

FIG. 19 depicts two lateral construct assemblies 200 such as would bearranged on the left and right sides of a spinal column (not shown)according to certain embodiments of the present disclosure. A retainingclip assembly 170 has been placed but not yet tightened around one ofthe lateral construct assemblies 200.

FIG. 20 depicts two lateral construct assemblies 200 joined by tworetaining clip assemblies 170S to form a derotation cluster 206according to certain embodiments of the present disclosure. In theembodiment of FIG. 20, a retaining clip assembly 170 has been installedover the proximal end of the knurled region of derotation tubes 120 andtightened. A second pair of short retaining clip assemblies 170S havebeen installed between the end derotation tubes 120 of the two lateralconstruct assemblies 200 across the distal portion of the knurled regionof derotation tubes 120, binding the two lateral construct assemblies200 into a single rigid derotation cluster 206.

The derotation cluster 206 can be used by the surgeon to modify thecurvature of the spine, e.g. alignment in the transverse plane, as wellas rotation in the coronal and sagittal planes. In certain methods ofalignment, the rod 112 is rotated using rod gripper (not shown) or a hexwrench (not shown) coupled to the hex ends 112A. In certain methods, oneor more of the locking screw assemblies 100 are tightened to retain thecoronal and sagittal alignment while the curvature of the spine isadjusted. Unilateral depression of the vertebral body using a derotationcluster 206 creates a lordosis in the spine, whereas lifting the entirederotation cluster 206 will enhance kyphosis. In certain embodiments,additional derotation assemblies 160 are used to provide additionalpoints of manipulation or restraint of one or both of the rods 112. Incertain methods, after the derotational maneuver has been completed,each locking screw assembly 100 is slowly tightened incrementally alongthe construct assemblies 200 to reduce the spine to the rods 112. If nofurther manipulation is required, the locking cap assemblies 100 can befully tightened to lock the housings 72 to the screw 40 in the currentorientation, and the tops of the elongated elements 76 can be broken offat the grooves 79 shown in FIG. 6B.

FIGS. 21A-21C depict a derotation sleeve assembly 210 according tocertain embodiments of the present disclosure. FIGS. 21A and 21B depictan assembled side view and an exploded isometric view, respectively, ofa derotation sleeve assembly 210. The derotation sleeve assembly 210includes a restraint shaft 220 and a restraint sleeve 230. The restraintshaft 220 has a hex tip 222 that is configured to engage the hexagonalrecess 50 of screw 40 and a collar 224 that is configured to slide overthe elongated elements 76 of housing 72, thereby centering the restraintshaft 220. In certain embodiments, a polyaxial screw (not shown)replaces the screw 70. The restraint sleeve 230 is similar to thederotation tube 180 in that it has the same flats 184 and interruptedthreads 186 as well as a hexagonal feature 128, with the addition of athreaded tip 232. In use, the restraint shaft is positioned above thescrew assembly 70 and advanced with the collar 224 sliding over theelongated elements 76 until the hex tip 22 engages the recess 50 of thescrew assembly 70. The restraint sleeve 230 is then placed over therestraint shaft 220 and advanced until the threaded tip 232 reaches thethreads 77 of the elongated elements 76, whereupon the restraint sleeve230 is rotated so that the threaded tip 232 engages the threads 77. Incertain embodiments, the restraint shaft 220 and the restraint sleeve230 are configured such that the hex tip 222 is forced into thehexagonal recess 50 as the restraint sleeve 230 advances in the distaldirection. When the restraint sleeve 230 is tightened, the threadedportion 44 of the screw assembly 70 is forced to remain in line with therestraint shaft 220 and restraint sleeve 230 to form a derotation sleeveassembly 210. In certain embodiments, the derotation sleeve assembly 210is used to accomplish derotation of one or more vertebra without use ofa rod 112.

FIG. 21C is an enlarged cross-section of the engagement of the restraintshaft 220 and restraint sleeve 230 with screw assembly 70. Hex tip 222is engaged in the recess 50 of the screw 40. The collar 224 surroundsthe elongated elements 76. The threaded tip 232 is engaged with thethreads 77 of the elongated elements 76 and is pressed against thecollar 224 thereby pressing the hex tip 222 in recess 50 which therebyplacing the housing 72 in tension against the screw head 40. In thisconfiguration, the restraint shaft 220 is forced into alignment with thescrew 40, and therefore restraint sleeve is therefore also aligned withscrew 40.

FIG. 22 depicts another derotation cluster 240 formed from a lateralconstruct assembly 202 and multiple derotation sleeve assemblies 210according to certain embodiments of the present disclosure. The lateralconstruct assembly 202 includes, in this embodiment, four derotationassemblies 160 with two locking nuts 188 each. The multiple derotationsleeve assemblies 210 have been coupled together with a retaining clipassembly 170 to form a lateral construct assembly 208. The lateralconstruct assemblies 202 and 208 have then been coupled together by apair of retaining clip assemblies 170S connected across the derotationassembly 160 and derotation sleeve assembly 210 at each end of thegroup, thereby forming the derotation cluster 240. In this embodiment,the retaining clip assemblies 170S were placed adjacent to the retainingclip assemblies 170 of the two lateral constructs, and the locking nuts188 were then tightened so as to capture both retaining clip assemblies170, 170S between them. In other embodiments, three locking nuts areinstalled on the end derotation assemblies 160 and derotation sleeveassemblies 210 so as to separately lock the two retaining clips 170 and170S to the center nut. In other embodiments, four locking nuts areinstalled on the end derotation assemblies 160 and derotation sleeveassemblies 210 so as to separately lock the two retaining clips 170 and170S between pairs of locking nuts 188.

FIGS. 23A-23B are perspective views of a polyaxial screw and capaccording to certain embodiments of the present disclosure. FIG. 23Adepicts a screw 310 with a threaded portion 314 and a spherical head 312that does not have the flats 48 but is otherwise, in certainembodiments, to the uniplanar screw 40 of FIGS. 7A-7B. FIG. 23B depictsa cap 320 that lacks the ears 66 while otherwise, in certainembodiments, similar to cap 60 of FIGS. 5A-5C.

FIGS. 23C-23D are front and side views of the polyaxial screw assembly300 according to certain embodiments of the present disclosure. In FIGS.23C and 23D, the polyaxial screw 310 and cap 320 have been assembledwith the housing 72 and pins 80 (not visible) to form a polyaxial screwassembly 300. It can be seen that the range of angular displacement 330of the threaded portion 314 with respect to the housing 72 is uniform inall directions.

FIGS. 24A-24C depict the insertion of a second rod 340 using thederotation cluster 240 of FIG. 22 according to certain embodiments ofthe present disclosure. In the embodiments of FIGS. 24A-24C, polyaxialscrew assemblies 300 have been used in the derotation sleeve assemblies210. In FIG. 24A, the retaining clip assemblies 170S and 170 have beenremoved and the derotation tube assemblies 160 have also been removedfrom the uniplanar screw assemblies 70, leaving an alignment system 110similar to that shown in FIG. 11D. Once the locking screw assemblies 100are tightened, which can be accomplished before the derotation tubeassemblies 160 are removed, the patient's spinal vertebrae will be heldin place while the second rod 340 is inserted. Additionally in FIG. 24A,the retaining posts of the derotation assemblies 160 have been unscrewedand removed from the derotation tubes 120 and the derotation tubes 120pulled up and off the polyaxial screw assemblies 300. The housings 72 ofthe polyaxial screw assemblies 300 are free to rotate and have beenindividually repositioned such that the U-shaped saddles of the housings72 are aligned.

In FIG. 24B, the second rod 340 has been placed in the pre-alignedhousings 72 of the polyaxial screw assemblies 300. Rod 340 is, in thisembodiment, generally similar in shape to the first rod 112. The use oftwo rods 112, 340 is sometimes preferred to a single rod 112 to provideadditional strength and stability in supporting and positioning thepatient's spinal vertebrae.

FIG. 24C depicts the addition of locking screw assemblies 100 to each ofthe polyaxial screw assemblies 300. The locking screw assemblies 100 areincrementally and sequentially tightened until the rod 340 is seated atthe bottom of the U-shaped saddle of housing 72 and secured to thehousing 72, which also locks the housing 72 to the screw 310 in thecurrent orientation. The upper portions of the elongated elements 76 canthen be broken off above the groove 79 for all screw assemblies 70, 300and the operation completed.

The disclosed systems and methods of use of screw assemblies, derotationassemblies, lateral constructs, and derotation clusters provide surgeonswith the capability to correct spinal deformity in the three primaryplanes of the human body. These various components and assemblies can beused in multiple combinations and techniques depending on the conditionof the patient and the preferences of the surgeon.

The previous description is provided to enable a person of ordinaryskill in the art to practice the various aspects described herein. Whilethe foregoing has described what are considered to be the best modeand/or other examples, it is understood that various modifications tothese aspects will be readily apparent to those skilled in the art, andthe generic principles defined herein may be applied to other aspects.Thus, the claims are not intended to be limited to the aspects shownherein, but is to be accorded the full scope consistent with thelanguage claims, wherein reference to an element in the singular is notintended to mean “one and only one” unless specifically so stated, butrather “one or more.” Unless specifically stated otherwise, the terms “aset” and “some” refer to one or more. Pronouns in the masculine (e.g.,his) include the feminine and neuter gender (e.g., her and its) and viceversa. Headings and subheadings, if any, are used for convenience onlyand do not limit the invention.

It is understood that the specific order or hierarchy of steps in theprocesses disclosed is an illustration of exemplary approaches. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the processes may be rearranged. Some of the stepsmay be performed simultaneously. The accompanying method claims presentelements of the various steps in a sample order, and are not meant to belimited to the specific order or hierarchy presented.

Terms such as “top,” “bottom,” “front,” “rear” and the like as used inthis disclosure should be understood as referring to an arbitrary frameof reference, rather than to the ordinary gravitational frame ofreference. Thus, a top surface, a bottom surface, a front surface, and arear surface may extend upwardly, downwardly, diagonally, orhorizontally in a gravitational frame of reference.

A phrase such as an “aspect” does not imply that such aspect isessential to the subject technology or that such aspect applies to allconfigurations of the subject technology. A disclosure relating to anaspect may apply to all configurations, or one or more configurations. Aphrase such as an aspect may refer to one or more aspects and viceversa. A phrase such as an “embodiment” does not imply that suchembodiment is essential to the subject technology or that suchembodiment applies to all configurations of the subject technology. Adisclosure relating to an embodiment may apply to all embodiments, orone or more embodiments. A phrase such an embodiment may refer to one ormore embodiments and vice versa.

The word “exemplary” is used herein to mean “serving as an example orillustration.” Any aspect or design described herein as “exemplary” isnot necessarily to be construed as preferred or advantageous over otheraspects or designs.

All structural and functional equivalents to the elements of the variousaspects described throughout this disclosure that are known or latercome to be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. No claim element is to be construedunder the provisions of 35 U.S.C. §112, sixth paragraph, unless theelement is expressly recited using the phrase “means for” or, in thecase of a method claim, the element is recited using the phrase “stepfor.” Furthermore, to the extent that the term “include,” “have,” or thelike is used in the description or the claims, such term is intended tobe inclusive in a manner similar to the term “comprise” as “comprise” isinterpreted when employed as a transitional word in a claim.

1.-44. (canceled)
 45. An alignment system comprising: a plurality ofscrew assemblies, each screw assembly comprising: a housing comprising aplurality of elongated elements forming a U-shaped saddle that isconfigured to accept a rod, at least one of the elongated elementscomprising threads on a portion of its surface facing another elongatedelement of the plurality of elongated elements; a screw extending intoand from the housing, the screw comprising a head and a threadedportion, the threaded portion configured to engage bone; a plurality offirst tubes configured to couple to the housings of respective screwassemblies and to extend beyond the housings when the first tubes arecoupled to the housings, each first tube having an externally threadedsegment configured to engage the threads of the at least one of theelongated elements of the respective screw assembly.
 46. The alignmentsystem of claim 45, further comprising a plurality of restraint shafts,each restraint shaft sized to extend through a respective one of theplurality of first tubes, each restraint shaft configured to engage apocket on the head of a respective screw of the plurality of screws suchthat the threaded portion of the screw is held in line with therestraint shaft.
 47. The alignment system of claim 46, wherein eachrestraint shaft has a hex tip and each pocket has a hexagonal recess.48. The alignment system of claim 46, wherein each restraint shaft has acollar attached to the restraint shaft and configured to slide over andsurround the elongated elements of the housing of the respective screwassembly.
 49. The alignment system of claim 45, wherein each first tubehas a first end, a second end, a first end portion, and at least oneflat, the second end being opposite the first end, the first end portionextending from the first end toward the second end and comprising theexternally threaded segment, the at least one flat extending along anouter surface of the first tube between the first end and the secondend.
 50. The alignment system of claim 45, further comprising aretaining clip configured to engage a row of the first tubes and, whenengaged with the first tubes, to resist displacement of the first tubeswith respect to each other.
 51. The alignment system of claim 45,wherein the retaining clip comprises two arms, and each of the two armscomprises a compressible pad disposed on a surface facing the other ofthe two arms.
 52. The alignment system of claim 45, further comprising aplurality of second tubes configured to engage the housings ofrespective screw assemblies and to extend beyond the housings when thesecond tubes are engaged with the housings, each second tube having afirst end, a second end opposite the first end, and an engagement sleeveattached to the second tube at the first end, the engagement sleeveconfigured to slide over the elongated elements of the housing of therespective screw assembly, the engagement sleeve having slots that fitover a rod extending through the housing, so as to prevent rotation ofthe second tube with respect to the respective screw assembly, andwherein the first tubes are sized to extend through the second tubes.53. The alignment system of claim 52, wherein each second tube has anabutment feature that seats against an abutment feature of a respectivefirst tube when both (i) the respective first tube extends through thesecond tube and (ii) each of the first tube and the second tube is fullyengaged with the housing of the respective screw assembly.
 54. Thealignment system of claim 53, wherein the abutment feature of the secondtube is hexagonal, and the abutment features of the first tube ishexagonal.
 55. The alignment system of claim 52, wherein each secondtube has at least one flat extending along an outer surface of thesecond tube between the first end and the second end.
 56. The alignmentsystem of claim 52, further comprising a retaining clip configured toengage a row of the second tubes and, when engaged with the secondtubes, to resist displacement of the second tubes with respect to eachother.
 57. The alignment system of claim 52, further comprising at leastone handle configured to couple removably to at least one of theplurality of second tubes such that, when coupled, a torque can beapplied through the handle to the second tube coupled thereto.
 58. Thealignment system of claim 57, wherein the handle comprises: a bodyhaving a passage; a handle post comprising: a coupler having an opencannula configured to engage the surgical tool; and a shaft fixedlyattached to the coupler, the shaft having a bore that passes into theopen cannula of the coupler, the shaft also configured to pass throughthe passage of the body; and a locking assembly comprising: a lockingnut; and a locking nut post fixedly attached to the locking nut andconfigured to engage the bore of the handle post shaft; wherein rotatingthe locking nut relative to the handle post shaft advances the lockingnut post through the bore of the shaft of the handle post and into theopen cannula of the coupler to secure the handle to the surgical tool.59. The alignment system of claim 58, wherein the open cannula ishexagonal in shape.
 60. The alignment system of claim 45, wherein eachscrew assembly comprises a locking cap assembly comprising: a slidingelement configured to fit around both elongated elements and to slidealong the elongated elements; and a threaded element disposed within thesliding element and configured to engage the threads of the at least oneelongated element; wherein each locking cap assembly is configured to becoupled to the housing of the respective screw assembly so as to capturea rod disposed within the U-shaped saddle of the housing and to displacethe rod along the U-shaped saddle as the threaded element is tightenedinto the housing until the rod is in contact with a bottom of theU-shaped saddle and then fixedly couple the rod to the respective screwassembly.
 61. The alignment system of claim 60, wherein each screwassembly comprises a cap coupled to the housing and configured to engagethe head of the screw such that when the cap is engaged with the screw,the relative angular displacement between the threaded portion and thecap is limited.
 62. The alignment system of claim 45, wherein each ofthe elongated elements of the plurality of elongated elements of eachscrew assembly comprises threads on a portion of its surface facinganother elongated element of the plurality of elongated elements. 63.The alignment system of claim 45, further comprising a rod configured toengage the plurality of screw assemblies by moving laterally into theU-shaped saddles.